1. Field of the Invention
The present invention relates generally to containers that include an internal module that adds heat to or removes heat from a material, such as a food, beverage, medicine, or the like, in the surrounding container.
2. Description of the Related Art
Containers may have integral modules for warming materials in the container, such as sake, coffee, or soup. Examples of such self-heating containers are disclosed in U.S. Pat. Nos. 5,461,867; 5,626,022; and 6,351,953 issued to Scudder et al. All patents, patent applications and other publications referenced in this application are hereby incorporated by reference herein in their entirety. Such containers typically include an outer can or body, in which the food or beverage is sealed, and an inner can or thermic module that contains two chemical reactants that are stable when separated from one another but, when they mix in response to actuation of the thermic module by a user, produce an exothermic reaction or, alternatively, an endothermic reaction and thereby heat or cool the contents of the container.
As part of the manufacturing process of such containers which are used for holding food and beverages, the containers must go through a sterilization process called “retort.” In general the retort process consists of subjecting the container and food contents to high temperatures and pressures. In a typical retort process, the container and contents are placed in a chamber for several minutes at 252 degrees Fahrenheit and two bars of pressure. Accordingly, the containers must be designed to withstand the retort process and still function properly.
The heating or cooling module (thermic module) is typically attached at one end of the cylindrical container body, and the elongated cylindrical reaction chamber portion of the module extends into the container body. This elongated portion functions as both a chamber in which to contain the reaction and a heat-exchanger for transferring heat between it and the surrounding contents of the container body. The thermic module has two chambers, each of which contains one of the chemical reactants, separated by a breakable barrier such as metal foil or a thin plastic film. Typically, one of the reactants is a liquid, and the other is in a solid powdered or granular form. Calcium oxide (commonly known as limestone) and water are examples of two reactants known to produce an exothermic reaction to heat the contents in such containers. Other combinations of reactants are known to produce endothermic reactions to cool the container contents. A cap containing the liquid reactant is disposed in the end of the thermic module attached to the container body. At one end of the cap is an actuator button that a user may press to initiate the heating or cooling. The barrier seals the other end of the cap. The cap has a pushrod or similar prong-like member that extends from the actuator button nearly to the barrier. Depressing the actuator button forces the prong into the barrier, puncturing it and thereby allowing the liquid reactant to flow into the solid reactant in the reaction chamber. The heat produced by the resulting exothermic reaction or absorbed by the resulting endothermic reaction is transferred between the reaction chamber of the thermic module and the contents of the container body by conduction. Exothermic reactions also typically generate a gas and/or steam, which is allowed to escape through vents in the end of the container. The user inverts the container and, when the contents have reached the desired temperature, consumes the contents. The second end of the container body has a seal or closure, such as a conventional beverage can pull-tab, that may be opened and through which the user may consume the heated or cooled contents.
A portion of the thermic module, such as the elongated cylindrical reaction chamber, may be unitarily formed with the outer can, as illustrated, for example, in U.S. Pat. No. 3,970,068, issued to Sato, and U.S. Pat. No. 5,088,870, issued to Fukuhara et al. The unitary container body is formed by providing a metal cylinder that is open at one end and closed at the other, and punching or deep-drawing a cavity in the closed end. A cap containing the liquid reactant is attached to the open end of the cavity. In other such containers, however, the elongated cylindrical reaction chamber may be separately formed and then attached to the container body by another manufacturing step. It would be desirable to provide an economical and reliable method for manufacturing this latter type of container.
The previously known elongated reaction chambers present several other design drawbacks. For one, the wall of the elongated reaction chamber separates the reaction chamber from the material contained in the container which is heated or cooled. This wall acts as an insulator which can slow the heating or cooling of the material by the thermic module. In addition, in response to the retort process, the chambers have suffered excessive deformation and cracking and have shown an inability to return to their expanded shape after being compressed during retort.
The retort process also has the potential to cause weakening or failure of the bond holding the breakable barrier separating the two chambers of the thermic module. The breakable barrier is typically heat sealed to a circular top edge of one chamber of the thermic module. During retort, the pressure of air expanding under the barrier tends to push the barrier upward into a dome shape which can cause the bond to weaken or detach.
Another problem associated with self-heating and self-cooling containers is that a person may attempt to consume the contents before the contents have been fully heated or cooled. That the person may be displeased by the resulting temperature of the beverage or other contents is not the only effect. A perhaps more serious effect is that a self-heating container may overheat and present a burn hazard if, after the user empties it of its contents, it continues to generate heat, because the contents act as a heat sink. It would be desirable to provide a self-heating container that prevents or inhibits a user from consuming the contents before the heating reaction has completed.
As disclosed in the above-referenced U.S. patents, the actuator button may be protected by a foil safety seal. An unbroken seal assures a person that the container has not been actuated and is thus ready for use. Also, the reactivity of typical chemicals such as calcium oxide may decrease if they absorb atmospheric moisture, such as could occur if the container were in storage or in transit for prolonged periods in a moist environment prior to use, and the seal inhibits exposure of the reactants to atmospheric moisture. To use the container, the user peels the foil seal off the container and discards it. The removal of the foil seal presents a disposal problem because the user may not be within a convenient distance of a trash receptacle. It would further be desirable to minimize disposal problems associated with self-heating and self-cooling containers.
The present invention is directed to improvements in self-heating containers which overcome these problems and deficiencies.